Various types of networks involving switches are in common use such as public and private telephone networks, local area networks (LAN) and wide area networks (WAN). LAN and WAN networks are digital and generally use asynchronous transfer mode (ATM) signals whereas telephone networks typically use analogue or synchronous digital signals (SONET). In ATM systems, the transmitted cells themselves carry the information that defines the destination of its payload. Similarly, in telephone systems, either analogue multitone or digital signals define the number being called which is used to set up the connection or, for digital lines, coded frames of data are transmitted synchronously to define the desired connection. In other networks, such as token ring systems, data is passed around sequentially from one station to the next until the header information in that cell is recognized. In telephone networks, a host of central offices control communications with groups of subscribers either on analog lines or on digital lines. Transmissions can take place between subscribers under the control of the same central office or between subscribers controlled by different central offices.
Broadband telecommunications networks contain hardware switches of various types and, for a given type, of various manufacturers. For example, such a network could contain frame, ATM and/or baseband analogue switches. A caller in one city making a call to a destination in a different city requires a way of setting up the various switches in order to communicate with the call destination. The caller would connect with a local address switch in the same city which, in turn, would contact and connect with a local address switch in another city and eventually connect with the local address switch in the destination city. The switches in one city could be primarily analogue switches while those in another city could contain ATM switches or a mixture of ATM and analogue switches. In addition, the ATM switches could be made by various manufacturers as could the analogue switches. In general switches of one manufacturer are controlled differently by different protocols from those of other manufacturers and, in addition, could be configured differently. In order to set up a call the central controller network through a switch controller would have to know the protocol and configuration for each of the different switches involved. Moreover, if a given switch were changed, likely the protocol for that switch and its configuration would be different from the previous switch. In this case the interface to the central network controller and associated switch controller would have to be rewritten and possibly interfaces to all other switches would have to be modified. Moreover, if it were desired to have communication between analogue and digital switches, some means of controlling an encoder/decoder has to be provided in addition to controlling the hardware switch to which it connects. Ordinarily inclusion of a requirement for codec control would require additional interfacing requirements for the central network controller thereby greatly increasing the complexity of the custom interfacing requirements between the central network controller and the switching controller.
Accordingly, it is an object of the invention to provide an improved means of communication across both analogue and digital switches in a network that permits communication between analogue terminals and digital terminals.